GB2060017A - Pressure-sensitive record colour-developing sheet - Google Patents

Description

1 GB 2 060 017 A 1

SPECIFICATION Pressure-sensitive record color-developing sheet

The present invention relates to a pressure-sensitive record colordeveloping sheet. More particularly, the present invention relates to a pressure-sensitive record color-deve loping sheet capable 5 of forming thereon clear images having a dark color and an excellent fight fastness.

Generally, a pressure-sensitive record material is composed of a combination of an upper sheet, on a surface of which are coated a number of pressure-rupturable micro-capsules containing a solution of an electron-donative colorless basic dye (color-forming agent), and a lower sheet, on a surface of which is coated an electron-accepting acid material (color-deve loping agent) capable of developing color images on the lower sheet when in contact with the colorless basic dye. The above-mentioned 10 type of pressure-sensitive record materials are disclosed in US Patent Nos. 2,730,456 and 2,730,457.

Generally, the color-forming agent is selected from triphenyimethane type color-forming dyes, for example, Crystal Violet lacton (CVL). This type of color-forming agent can produce clear blue-violet images the moment it contacts the acid color-forming agent. However, the thus produced color images exhibit a very poor light fastness to the point that, when exposed to sun light or ultraviolet rays, the color 15 images are rapidly faded within a short time and, finally, disappear. Also, the color images consisting of the triphenyimethane type dye exhibit such a disadvantage that the color images disappear when they contact water during the storage thereof. In order to decrease the above-mentioned disadvantages of the color images, it has been attempted to mix a methylene blue type colorless dye which is capable of producing a color image having a relatively high fight fastness into the triphenyimethane type color dye. 20 However, it was found that this cannot eliminate the disadvantages of the triphenyl methane type dye per se. Also, the mixture exhibits such a disadvantage that, during a long period of storage of the color images, the color of the images alters from dark navy blue to light green.

The above-mentioned disadvantages of the conventional pressure-sensitive record material is remarkably exhibited when a solid acid, for example, attapulgite or acid terra abla, is used as a color- 25 developing agent. In order to eliminate the above-mentioned disadvantage of the solid acid, various approaches were attempted.

In one approach, various acid clay type mineral materials, kaolin and zeolite were treated physically by heat or chemically with an acid or alkali, to provide, for example, activated clay, fired kaolin.

and fired activated clay. In another of the approaches, the abovementioned solid acids were used 30 together with various inorganic compounds, for example: a water-insoluble salt of cobalt, manganese or lead (Japanese Patent Application Publication No. 41-16822(1966); a watersoluble salt of zinc, cadmium, mercury, calcium, magnesium, strontium, manganese, cobalt or nickel (Japanese Patent Application Publication No. 42-20,143(1967W a metal hydroxide or carbonate (Japanese Patent Application Publication No. 41-16,262(1966)); an alkali neutralizationproduct of a hydroclorate or 35 sulfate of aluminium, manganese or zinc (Japanese Patent Application Publication No.

43-10,091(1978)); an alkali neutralization product of a hydrochlorate or oxide of tin, zinc or aluminium (Japanese Patent Application Publication No 42-25,250(1967)); a complex of a cupric compound with ammonia (Japanese Patent Application Publication No. 34-28, 4310968W a complex of a colloidal zinc hydroxide with water glass (Japanese Patent Application Publication No.

44-2,1930969W a treatment product of zinc oxide with ammonia (Japanese Patent Application Publication No. 46-9,290(197 M; a metal nitrhe (Japanese Patent Application Publication No.

51-15,777(1976)); a mixture of a rhodanate with a metal compound (Japanese Patent Application Publication No. 48-12,254(1973)), or; a mixture of an organic cyanamide compound with a metal compound (Japanese Patent Application publication No. 50-16,968(1975)). In still another approach, 45 microcapsules containing therein a mixture of urea or thiourea, zinc chloride and a solvent, are used as a color-developing agent (Japanese Patent Application Laying-open No. 50-65, 318(1975)). In further approaches, there were used as a color-developing agent effective for improving the water fastness and light fastness of the color images, in place of the inorganic color developing agents, such as clay: an organic compound, for example, a phenol compound (Japanese Patent Application Publication No. 50 40-9,309(1965)); a condensation product of a phenol compound with an aldehyde compound, that is, a novolak resin (Japanese Patent Application Publication Nos. 42-20, 144(1967)) and 46-37,451(197 1); or an aromatic carboxylic acid, for example, benzoic acid, naphthoic acid or salicylic acid, an acid derivative of the carboxylic acid or a metal compound of the carboxylic acid or its acid derivative (Japanese Patent Application Publications Nos. 49-10, 856(1974), 49-13,451(1974) 55 and 52-1,327(1979)). In the other approaches, the above-mentioned organic acid substance was used together with an inorganic color developing agent, such as clay (Japanese Patent Application Publication No. 50-17,888(1975)), or the above-mentioned inorganic color-deve loping agent was used together with urea or thioruea, and a chloride of zinc, vanadium, chromium, manganese, iron, cobalt, nickel or copper (Japanese Patent Application Laying-open No. 51- 111,113(1976)).

However, the above-mentioned approaches failed to provide color images having satisfactory color depth, water fastness and/or light fastness.

The object of the present invention is to provide a pressure-sensitive record color-developing sheet capable of producing clear color images having an excellent color density and exhibiting an 60' 2 GB 2 060 017 A 2 excellent water fastness and light fastness.

The above-mentioned object can be attained by the pressure-sensitive record color-developing sheet of the present invention, which comprises a substrate layer and a color-deve loping layer formed on a surface of the substrate layer and containing an acid color-developing agent, an agent for promoting color-development and preventing color-fading of color images, and a binder, and which is characterized in that the color development- promoting, color fading-preventing agent contains at least one thiourea compound and zinc oxide and/or zinc hydroxide.

In the pressure-sensitive record color-developing sheet of the present invention, the substrate may be formed from the same material as that used in conventional pressure-sensitive record color- developing sheets. That is, the substrate may be made of a paper or synthetic polymer film sheet.

The acid col or-deve loping agent usable for the present invention may consist of at least one member selected from inorganic acid colordeveloping agents, for example, acid terra abla, activated clay, aluminium silicate, talc, attapulgite, kaolin and zeolite, and organic acid color-developing agents, for example, condensation products of phenol compounds with aldehyde compounds, that is, novolak resins.

The phenol compounds usable for producing the phenol compound-aldehyde compound condensation products may be selected from phenol, pphenylphenol, p-ten-butylphenol, p-npropylphenol, p-n-butylphenol, pisobutyl phenol, p-n-octylphenol, p-benzylphenol and cresol. The aldehyde compound usable for the condensation products, are selected from formaldehyde, paraformaldehyde and acetaidehyde.

The binder to be contained in the color-developing agent is not limited to a special type of binder, unless the binder hinders attainment of the object of the present invention. Usually, the binder comprises at least one member selected from water-soluble polymers, for example, starch, polyvinyl alcohol, gum arabic, carboxymethyl cellulose and hydroxyethyl cellulose, and; water-emulsive polymers, for example, styrene-butadiene copolymers, methyl methacrylate-butadiene copolymers and acrylic polymers. The amount of the binder to be contained in the color-developing sheet is preferably in a range of from 5 to 40% by dry weight based on the weight of the acid color-developing agent.

It is essential for the pressure-sensitive record color-developing sheet of the present invention that the color development-promoting, color fading-preventing agent contain at least one thiourea compound and zinc oxide and/or zinc hydroxide. Usually, the thiourea compound is used in an amount of 30 from 1 to 100%, based on the weight of the acid color-developing agent. Also, it is preferable that the zinc compound be used in an amount of from 1 to 100%, based on the weights of the acid color developing agent.

The thiourea compound may be selected from the group consisting of thiourea, Wethyl thiourea, N-phenyl thlourea, W(a-naphthyl)thioure.a, N,N-diethyl thiourea, N,N- diphenylthiourea, N-phenyl-N,N'- 35 dimethyl thiourea, N-phenyl-N'-benzyl thiourea, N-phenyl-N-octadecyl thiourea, N-phenyl-N-(p dimethylaminophenyl) thiourea, W(p-tolyl)-N'-cyclohexyl thiourea, W(p- rnethoxyphenyl)-N'-alkyl thiourea, N-phenyl-M-(a-pyridyl) thiourea, W(m-chlorophenyll)-N'-phenyl thiourea, W(P-naphthyl) N',N'-penta methylene thiourea, N-hexamethylene-bis(N'-phenyl)thiourea, N, N'-bis(p di methyl am inophenyl)thiou rea, N,N'-ethylene thiourea-(2- imidazolidine), allyl thiourea and cyclohexyl 40 thiourea. The preferable thiourea compound is selected from thlourea, Walkylthioureas and Waryl thioureas. It is preferable that the thiourea compound be used in an amount of from 0.5 to 20 motes, more preferably, from 2 to 16 moles, per mole of the zinc compound.

The pressure-sensitive record color-developing sheet can be produced by the following process.

First, a predetermined amount of a thiourea compound is dissolved in water. In this case, the water may contain a dispersing agent consisting of a sodium pyrophosphate, sodium metaphosphate and/or sodium silicate, for dispersing the inorganic acid color- developing agent. Next, a predetermined amount of a zinc compound is dispersed in the above-mentioned solution, and the pH of the resultant aqueous solution-dispersion is adjusted to alkaline, preferably, 8.0 or more, by using an alkali, such as sodium hydroxide, ammonia or water glass.

Next, predetermined amounts of a color-deve loping agent and a binder are mixed into the a - queous solution-dispersion. Thereafter, the pH of the resultant aqueous mixture is adjusted to alkaline.

Next, the aqueous mixture containing the color-deve loping agent, thiourea compound, zinc compound and binder is applied onto a surface of the substrate, and then, dried. The dried color- developing layer preferably has a weight of from 1 to 10 g/m', more preferably, from 2 to 6 g/m'.

The colourless cgior forming agent capable of forming color images on the color-developing sheet of the present invention may consist of at least one colorless basic dye selected from Crystal violet lactone, Benzoyl lueco methylene blue, Malachite green lacton and Rhodamine-P-lactum. When the color-forming agent is brought into contact with the color-developing layer of the color-developing sheet of the present invention, the colorless basic dye is converted in a moment into coloring dye so as 60 to form color images. The color images formed on the color-developing sheet have a very remarkable color depth. Therefore, in the color-developing sheet of the present invention, the amount of the color developing layer may be smaller than that of the conventional color- developing layer. Also, the color images formed on the color-developing sheet of the present invention can exhibit extremely excellent light fastness and, therefore, can be stored over a very long period of time without color-fading of the 65 ? 3 GB 2 060 017 A color images.

The color-developing layer of the present invention may contain any additives which can be contained in the conventional color-developing layer, for example, a filler such as calcium carbonate, talc and clay; ultraviolet ray-absorbing agent; antioxidant and coloring material. Also, the aqueous mixture for forming the color-deve loping layer may contain a surface active agent, for example, dispersing agent and anti-foaming agent.

The present invention will be further illustrated by the following examples.

In the examples, upper sheets containing the color-forming agent, which sheets had been prepared by the following method, were used for forming color images on the color-developing sheets.

A solution was prepared by dissolving 21 parts of Crystal violet lacton in 9 parts of Benzoyl lueco 10 methylene blue in 370 parts of a alkylated naphthalene oil. The solution was converted into a number of microcapsules by a coacervation method. A dispersion of the microcapsules was applied onto a surface of a sheet having a weight of 40 g/M2, and dried. The dried microcapsule layer had a weight of 4 g/m'.

EXAMPLES 1 to 8 In each of the Examples 1 to 8, an aqueous mixture for forming a color- developing layer was 15 prepared in the following manner.

One part by weight of a dispersing agent consisting of sodium hexametaphosphate was dissolved in 220 to 260 parts by weight of water and 30 parts by weight of a 10% starch solution were added to the above-prepared solution. Thereafter, a thiourea compound as indicated in Table 1 was added in an amount as indicated in Table 1 and, then, a zinc compound as indicated in Table 1 was added in an 20 amount as indicated in Table 1 into the solution. The pH of the resultant mixture was adjusted to 9.0 to 9.5 by using a 28% ammonia aqueous solution while stirring the mixture. Next, 100 parts by weight of an activated clay were added to the mixture while stirring the mixture. The resultant mixture was homogenized by using a homomixer. Next, 26 to 35 parts by weight of a 50% aqueous latex of a styrene-butadiene copolymer were mixed into the homogenized mixture and, then, the pH of the 25 mixture was adjusted to 9.5 by using a 28% ammonia aqueous solution. A coating liquid was obtained.

The coating liquid was applied onto a sheet of paper having a weight of 40 g/M2 and the coated layer was dried so as to form a color-forming layer having a dry weight of 6 g/M2.

The properties of color images formed on the color-forming sheet are indicated in Table 1.

The color density of the color images was determined by subjecting the color images just after the 30 color-developing procedure to a color density measurement by using a co- for-densitometer. The hue of the color images just after the color-developing procedure was measured by using a digital color difference meter and expressed in the following manner.

A: Blue (desired color) B Greenish Blue (slightly insufficient in blue hue) 35 C Bluish Green (considerably insufficient in blue hue) D: Green (substantially no or very small blue hue) The light fastness test was carried out by exposing the color images to a fading meter for 4 hours and the exposed color images were compared with non-exposed color images to determine the light fastness of the color images. The light fastness of the color images was expressed in the following 40 manner.

Good: no change in hue or very slight change in blue hue on the exposed color images.

Slightly poor: considerable change in blue hue on the exposed color images.

Poor: remarkable change in blue hue on the exposed color images.

EXAMPLE 9

One part by weight of a dispersing agent consisting of sodium hexa meta phosphate was dissolved in 140 parts by weight of water. 30 parts by weight of a 10% aqueous solution of starch were added to the dispersing agent solution. Next, thiourea in the amount indicated in Table 1 was added to the solution and, then, zinc oxide in the amount indicated in Table 1 was added to the solution. The pH of the resultant mixture was adjusted to a range of from 9.0 to 9.5 by adding a 28% ammonia aqueous 50 solution while sirring the mixture. Next, 50 parts by weight of activated clay were added to the mixture.

The resultant mixture was homogenized by using a homomixer.

Separately, 50 parts by weight of a p-phenyl phenol novolak resin were dispersed in 116 parts by weight of water by using a ball mill. The novolak dispersion was mixed into the aqueous mixture and, then, the resultant mixture was mixed with 25 parts by weight of a 50% styrene-butadiene copolymer 55 4 GB 2 060 017 A 4 latex. The pH of the mixture was adjusted to 9.5 by using a 20% ammonia aqueous solution. A coating liquid was obtained.

The coating liquid was applied onto a surface of a sheet of paper having a weight of 40 g/M2 and dried. The weight of the dried color-forming layer was 6 g/M2.

The properties of the color images formed on the cbio-r-forming layer are indicated in Table 1. 5 0.

JC d i (n TABLE 1

Color-developing agent Zinc compound Thiourea compound Molar ratio Color images Of Example Amount Amount Amount Zinc compound/ Color Light No. Type (part) Type (part) Type (part) Thiourea compound densi ty Hue fastness 1 Act! vated 100 Zn(Offi2 15 Thiourea 5 415 0.89 A Good clay 2 100 20 30 1/3 0.87 A 3 100 4 12 114 0.93 A 4 100 8 Wethyl 30 115 0.75 A thiourea 100 8 Allyl- 23 1/8 0.84 A thiourea 6 100 8 Thiourea 22 114 0.80 A 7 100 5 4 ill 0.76 A 8 100 ZnO 8 15 112 0.86 A 9 Activated 50 clay 8 15 112 0.79 A Novolak 50 resin G) m NJ 0 0) 0 0 -4 al 6 GB 2 060 017 A 6 COMPARATIVE EXAMPLES 1 to 5 In each of the Comparative Examples 1 to 5, the same procedures as those mentioned in Example 1 were followed, except that the color forming agent, the zinc compounds and urea type compound of the types as indicated in Table 2 were used in amounts as indicated in Table 2. The properties of the color images formed on the comparative color-developing sheet are indicated in Table 2.

I.i TABLE 2

Color-developing agent Zinc compound Urea type Color images Comparative Amount Amount Amount Color Example No. Type (part) Type (part) Type (part) density Hue Light fastness Activated 100 0.77 B Poor clay 2 91 100 Thiourea 15 0.50 B 3 09 100 Zn(OH), 15 - 0.67 B 4 ZnCl, 15 Tiliourea 15 0.18 c (very light greenish blue) Zn(Offi,. 50 Thiourea 20 0.15 c (very I ight) greenish blue) 9 1 Y 1 8 GB 2 060 017 A 8

Claims (8)

1. A pressure-sensitive record color-developing sheet comprising a substrate layer and a colordeveloping layer formed on a surface of said substrate layer, and containing an acid color-developing agent, an agent for promoting color-development and preventing color-fading, and a binder, characterized in that said color-development promoting, color-fading preventing agent contains at least one thiourea compound, and zinc oxide and/or zinc hydroxide.

2. A pressure-sensitive record color-deve loping sheet as claimed in claim 1, wherein said thiourea compound and said zinc-containing compound are used in amounts of from 1 to 100% and from 1 to 100%, based on the weight of said color-developing agent, respectively.

3. A pressure-sensitive record- color-developing sheet as claimed in claim 1 or 2 wherein said acid 10 color-deve loping agent contains at least one member selected from the group consisting of acid terra abla, activated clay, aluminium silicate, talc, attapulgite, kaolin, zeolite and condensation products of phenol compounds with aldehyde compounds.

4. A pressure-sensitive record color-developing sheet as claimed in claim 1, 2 or 3 wherein said substrate consists of a member selected from the group consisting of paper and synthetic p olymerfilms 15 and sheets.

5. A pressure-sensitive record, color-developing sheet as claimed in any one of claims 1 to 4 wherein said binder comprises at least one member selected from the group consisting of starch, polyvinyl alcohol, gum arabic carboxymethyl cellulose, hydroxyethyl cellulose, styrene-. butad. iene copolymers, methyimethacrylate-butadiene copolymers and acrylic polymers.

6. A pressure-sensitive record color-developing sheet as claimed in claim 5, wherein the amount of said binder is in a range of from 5 to 40% based on the weight of said acid color-developing agent.

7. A pressure-sensitive record color-developing sheet as claimed in any one of claims 1 to 6 wherein said thiourea compound is selected from the group consisting of thiourea, Wethyl thiourea, N phenyl thiourea, W(a-naphthyl) thiourea, N,N-diethyi thiourea, N,N- dipherlyl thiourea, N-phenyl-N,W- 25 dimethyl thiourea, N-pheny1W-benzyi thiourea, N-pheny1W-octadecyl thiourea, N-pheny1W-(p dimethylaminophenyf)thiourea, W(p-tolyOW-cyclohexyl thiourea, N-(p- methoxyphenyi)-N'-allyl thiourea, N-pheny1W(a-pyridyl) thiourea, W(m-ch lorophenyl)-N '-phenyl thiourea, N-(p-naphthyi) N',N'-penta methylene thiourea, N-h exa methyl ene-bis N'-pheni) thiour'ea, N,Wbis(p dimethylaminophenyl) thiourea, N,NI-etylene thiourea-(2-imidazolidine), allyl thiourea and cyclohexyl 30 thiourea.

8. A pressure sensitive record color-developing sheet as claimed in any one of claims 1 to 7 wherein said thiourea compound is used in an amount of from 0.5 to 20 moles per mole of said zinc containing compound.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981.. Published by the Patent Office,25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

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